[Merged by Bors] - Deploy default and support custom affinities

[razvan]

Description

Part of https://github.com/stackabletech/issues/issues/323

CI https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/spark-k8s-operator-it-custom/68/

Review Checklist

• [ ] Code contains useful comments
• [ ] CRD change approved (or not applicable)
• [ ] (Integration-)Test cases added (or not applicable)
• [ ] Documentation added (or not applicable)
• [ ] Changelog updated (or not applicable)
• [ ] Cargo.toml only contains references to git tags (not specific commits or branches)
• [ ] Helm chart can be installed and deployed operator works (or not applicable)

Once the review is done, comment bors r+ (or bors merge) to merge. Further information

[razvan]

bors merge

[bors[bot]]

Pull request successfully merged into main.

Build succeeded:

• All tests passed